1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a driving apparatus and method of a liquid crystal display device that is adaptive for preventing a picture quality defect caused by non-uniformity of a sub-pixel signal polarity in accordance with the number of output channels of a data drive circuit.
2. Description of the Related Art
Generally, a liquid crystal display device controls the light transmissivity of liquid crystal using an electric field, to display a picture. For this, the liquid crystal display device includes a liquid crystal display panel where liquid crystal cells are arranged in a matrix shape and a drive circuit to drive the liquid crystal display panel.
In fact, the liquid crystal display device, as illustrated in FIG. 1, includes a liquid crystal display panel 6 that displays a picture in accordance with the polarity pattern of a sub-pixel signal; a data TCP (Tape Carrier Package) 8 on which a data D-IC (Drive Integrated Circuit) 10 is mounted for driving data lines of the liquid crystal display panel 6; a gate TCP 4 on which a gate D-IC 12 is mounted for driving gate lines of the liquid crystal display panel 6; and a timing controller 30 to drive the data IC's 10 and the gate D-IC's 12.
The liquid crystal display panel 6 includes a liquid crystal layer formed between an upper substrate 5 and a lower substrate 3, and a spacer to maintain a distance between the upper substrate 5 and the lower substrate 3. A color filter, a common electrode, a black matrix and so on are formed in the upper substrate 5 of the liquid crystal display panel 6. The common electrode may be formed in the lower substrate 3 in accordance with a liquid crystal layer mode of the liquid crystal display panel 6. Further, the lower substrate 3 of the liquid crystal display panel 6 includes a thin film transistor formed at each crossing of the gate lines and the data lines, and a liquid crystal cell connected to the thin film transistor. A gate electrode of the thin film transistor is connected to any one of the gate lines (the horizontal lines), and a source electrode is connected to any one of the data lines (the vertical lines). The thin film transistor supplies a pixel signal from the data line to the liquid crystal cell in response to a scan signal from the gate line. The liquid crystal cell includes a pixel electrode connected to a drain electrode of the thin film transistor, and a common electrode facing the pixel electrode with a liquid crystal layer therebetween. The liquid crystal cell drives the liquid crystal layer in response to the pixel signal supplied to the pixel electrode, thereby controlling the light transmissivity.
In order to drive the liquid crystal cells on the liquid crystal display panel 6, an inversion driving method is used such as a frame inversion system, a line inversion system and a dot inversion system. In the driving method of the frame inversion system, the polarity of the pixel signals supplied to the liquid crystal cells on the liquid crystal display panel 6 is inverted whenever a frame is changed. In the driving method of the line inversion system, the polarity of the pixel signals supplied to the liquid crystal cells is inverted in accordance with the line (column) on the liquid crystal display panel 6. The dot inversion system has a pixel voltage signal supplied of which a polarity is contrary to the polarity of the pixel signals supplied to the liquid crystal cells that are adjacent to the liquid crystal cells on the liquid crystal display panel 6 in their vertical and horizontal directions, and the polarity of the pixel signals supplied to all the liquid crystal cells on the liquid crystal display panel 6 is inverted every frame. The drive of such an inversion method is performed by having the data D-IC's 10 respond according to a polarity signal POL supplied to each of the data D-IC's 10 from the timing controller 30.
The liquid crystal display device of the related art is driven by a frame frequency of 60 Hz. But, in a low power-consumption system like a notebook, the frame frequency is lower, between 50 Hz to 30 Hz. As the frame frequency decreases, a greenish phenomenon is produced even in the dot inversion system which provides the best picture quality. Thus, a horizontal 2-dot inversion system and a square inversion system have been suggested.
In the horizontal 2-dot inversion system, the polarity of the sub-pixel signal is changed on a per-dot basis in a vertical direction, but is changed each two dots in a horizontal direction. In addition, the polarity of the pixel signals supplied to all the liquid crystal cells on the liquid crystal display panel 6 is inverted every frame. In the square inversion system, the polarity of the sub-pixel signal is changed by the two dots in both a vertical direction and a horizontal direction. In addition, the polarity of the pixel signals supplied to all the liquid crystal cells on the liquid crystal display panel 6 is inverted every frame.
In this way, in the one dot inversion system, the polarity of the sub-pixel signal supplied to the liquid crystal cell repeats by two liquid crystal cells in the horizontal direction. On the other hand, in the two dot inversion system, the polarity of the sub-pixel signal supplied to the liquid crystal cell repeats by four liquid crystal cells in the horizontal direction, and in the square inversion system, the polarity of the sub-pixel signal supplied to the liquid crystal cell repeats by four liquid crystal cells in the vertical and horizontal directions.
The timing controller 30 generates gate control signals such as GSP, GSC, GOE and so on that control the drive of the gate D-IC's 4, and generates data control signals such as SSP, SSC, SOE, POL and so on that control the drive of the data IC's 10. Further, the timing controller 30 aligns the data signal supplied from the system to fit the data signal for the drive of the liquid crystal display panel 6, and supplies the aligned data signal to a plurality of data D-IC's 10.
The timing controller 30 is mounted on a data PCB (printed circuit board) 20. The data PCB 20 is connected to an external system through a user connector. On the data PCB 20, there are various signal lines that supply various control signals and data signals from the timing controller 30 to each of the data D-IC's 10 and the gate D-IC's 12.
Each of the gate D-IC's 12 is mounted on the gate TCP 4. The gate D-IC 12 mounted on the gate TCP 4 is electrically connected to the gate pads of the liquid crystal display panel 6 through the gate TCP 4. The gate D-IC's 12 sequentially drive the gate lines of the liquid crystal display panel 6 by the one horizontal period (1H). The gate TCP 4 is connected to a gate PCB 26. The gate PCB 26 supplies the gate control signals supplied from the timing controller 30 through the data PCB 20 to the gate D-IC's 12 through the gate TCP 4.
Each of the data D-IC's 10 is mounted on each of the data TCP 8. The data D-IC 10 mounted on the data TCP 8 is electrically connected to the data pads of the liquid crystal display panel 6 through the data TCP 8. The data D-IC's 10 convert a digital pixel data into an analog pixel signal to supply the converted pixel signal to the data lines of the liquid crystal display panel 6 by the one horizontal period (1H).
In this way, in the driving device of the related art liquid crystal display device, the repetition period of the sub-pixel signal polarity becomes uniform or non-uniform in accordance with the number of the output channels of the data D-IC 10 and the inversion method of the polarity pattern of the sub-pixel signal supplied to the liquid crystal display panel 6.
For example, the data D-IC 10 having even-numbered output channels might produce output such that the polarity of the sub-pixel signal has the polarity pattern of the one dot inversion system regardless of the number of output channels of the data D-IC. 10. In other words, as illustrated in FIG. 2, if the pixel signal having the polarity pattern of the one dot inversion system is supplied to the liquid crystal display panel 6 using the data D-IC's 10 having 384 (a multiple of 4) output channels (Ch1 to Ch384), the polarity of the sub-pixel signal between the last output channel Ch384 of the odd-numbered data D-IC 10 and the first output channel Ch1 of the even-numbered data D-IC 10 is not equal but inverted. That is, the polarity of the sub-pixel signal outputted from the last output channel Ch384 of the odd-numbered data D-IC 10 is “−”, and the polarity of the sub-pixel signal outputted from the first output channel Ch1 of the even-numbered data D-IC 10 is “+”.
In addition, if the pixel signal having the polarity pattern of the one dot inversion system is supplied to the liquid crystal display panel 6 using the data D-IC's 10 having 414 (which is not a multiple of 4, but is a multiple of 2) output channels (Ch1 to Ch414), the polarity of the sub-pixel signal between the last output channel Ch414 of the odd-numbered data D-IC 10 and the first output channel Ch1 of the even-numbered data D-IC 10 is not equal but inverted. Accordingly, the driving method of the liquid crystal display panel 6 by the one dot inversion system using the data D-IC 10 having a number of output channels that is a multiple of 2, is driven to have the polarity pattern of the exact one dot inversion system regardless of the number of output channels of the data D-IC 10.
On the other hand, as illustrated in FIG. 3, if the pixel signal having the polarity pattern of the horizontal two dot inversion system is supplied to the liquid crystal display panel 6 using the data D-IC's 10 having 384 (a multiple of 4) output channels (Ch1 to Ch384), the polarity of the sub-pixel signal between the last two output channels Ch 383, Ch384 of the odd-numbered data D-IC 10 and the first and second output channels Ch1, Ch2 of the even-numbered data D-IC 10 is not equal but inverted. In other words, the polarity of the sub-pixel signal outputted from the last two output channels Ch383, Ch384. of the odd-numbered data D-IC 10 is “−−”, and the polarity of the sub-pixel signal outputted from the first and second output channels Ch1, Ch2 of the even-numbered data D-IC 10 is “++”. Accordingly, the driving method of the liquid crystal display panel 6 by the two dot inversion system using the data D-IC 10 having a number of output channels that is a multiple of 4, is driven to have the polarity pattern of the exact horizontal two dot inversion system regardless of the number of output channels of the data D-IC 10.
Furthermore, as illustrated in FIG. 4, if the pixel signal having the polarity pattern of the horizontal two dot inversion system is supplied to the liquid crystal display panel 6 using the data D-IC's 10 having 414 (not a multiple of 4, but a multiple of 2) output channels (Ch1 to Ch414), the polarity of the sub-pixel signal between the last two output channels Ch 413, Ch414 of the odd-numbered data D-IC 10 and the first and second output channels Ch1, Ch2 of the even-numbered data D-IC 10 is equal.
For example, if the polarity of the sub-pixel signal outputted from the first and second output channels Ch1, Ch2 of the data D-IC 10 having a number of output channels that is a multiple of 2, starts with “++”, the polarity of the sub-pixel signal outputted from the first and second output channels Ch1, Ch2 of each of the odd-numbered data D-IC 10 and the even-numbered data D-IC 10 starts with “++”. Because of this, the polarity of the sub-pixel signal outputted from the last two output channels Ch413, Ch414 of the odd-numbered data D-IC 10 is “++”, and the polarity of the sub-pixel signal outputted from the first and second output channels Ch1, Ch2 of the even-numbered data D-IC 10 is “++”. Accordingly, in driving the liquid crystal display panel 6 by the two dot inversion system using the data D-IC 10 having a number of output channels that is a multiple of 2, the same polarity of the sub-pixel signal is supplied to the four liquid crystal cells which are a bordering area between the adjacent data D-IC's 10.
Therefore, as illustrated in FIG. 4, if the number of the output channels of the data D-IC 10 is not a multiple of 4, the repetition period of the sub-pixel signal polarity is non-uniform at a bordering area A between the adjacent data D-IC's 10 to generate a picture quality defect such as a vertical line in the driving apparatus of the liquid crystal display device using the related art horizontal two dot inversion system.
On the other hand, as illustrated in FIG. 5, if the pixel signal having the polarity pattern of the square inversion system using the data D-IC's 10 having 414 (not a multiple of 4, but a multiple of 2) output channels Ch1 to Ch414, the polarity of the sub-pixel signal between the last two output channels Ch 413, Ch414 of the odd-numbered data D-IC 10 and the first and second output channels Ch1, Ch2 of the even-numbered data D-IC 10 of the jth (where j is a positive integer) and (j+1)th horizontal lines is equal. For example, if the polarity of the sub-pixel signal outputted from the first and second output channels Ch1, Ch2 of the data D-IC 10 having a number of output channels that is a multiple of 2, starts with “++”, the polarity of the sub-pixel signal outputted from the first and second output channels Ch1, Ch2 of each of the odd-numbered data D-IC 10 and the even-numbered data D-IC 10 of each of the jth and (j+1)th horizontal lines starts with “++”. Because of this, the polarity of the sub-pixel signal outputted from the last two output channels Ch413, Ch414 of the odd-numbered data D-IC 10 of each of the jth and (j+1)th horizontal lines is “++”, and the polarity of the sub-pixel signal outputted from the first and second output channels Ch1, Ch2 of the even-numbered data D-IC 10 of each of the jth and (j+1)th horizontal lines is “++”. Accordingly, in driving the liquid crystal display panel 6 by the square inversion system using the data D-IC 10 having a number of output channels that is a multiple of 2, the same polarity of the sub-pixel signal is supplied to the eight liquid crystal cells which are a bordering area between the adjacent data D-IC's 10.
Therefore, as illustrated in FIG. 5, if the number of the output channels of the data D-IC 10 is not a multiple of 4, the repetition period of the sub-pixel signal polarity is non-uniform at a bordering area A between the adjacent data D-IC's 10 to generate a picture quality defect such as a vertical line in the driving, apparatus of the liquid crystal display device using the related art square inversion system.